1. Field of the Invention
The present invention relates to an optimal recording method for optical recording media, and more particularly to an optimal recording method for optical recording media which is capable of recording information about optimum recording conditions on an optical recording medium in order to allow a subsequent recording of data on the optical recording medium at an optimum recording power, based on the recorded optimum recording condition information. The present invention also relates to an optical recording medium recorded with such optimum recording condition information.
2. Description of the Conventional Art
FIG. 1 illustrates the configuration of an optical recording/reproducing apparatus for recording data on an optical recording medium and reproducing the recorded data.
As shown in FIG. 1, this optical recording/reproducing apparatus includes a digital recording signal processing unit 30a for adding an error correction code (ECC) to input digital data, thereby converting the input digital data into a recording format, a channel bit encoder unit 40 for re-converting the data, converted into the recording format, into a bit stream, an optical driver unit 50 for outputting a light amount drive signal, an optical pick-up unit 11 for recording a desired signal onto an optical recording medium 10 in accordance with the light amount drive signal, and detecting a recording signal from the optical recording medium 10, and a drive unit 80 for driving the optical pick-up unit 11 and a motor M. The optical recording/reproducing apparatus further includes an R/F unit 60 for filtering a signal detected by the optical pick-up unit 11, conducting a waveform shaping for the filtered signal, and converting the resultant signal into a binary signal, a servo unit 70 for controlling the driving of the drive unit 80, based on signals indicative of tracking errors and focusing errors generated in the optical pick-up unit 11, along with the rotating speed of the optical recording medium 10, a digital reproduced signal processing unit 30b for recovering the binary signal into original data at a clock synchronizing with the binary signal, and a microcomputer 100 for controlling the recording/reproducing procedure.
Now, an operation of the above mentioned optical recording/reproducing apparatus will be described in conjunction with FIG. 1.
When a data recording request is inputted to the microcomputer 100 under the condition in which an optical recording medium 10 is loaded in a tray not shown, the optical recording/reproducing apparatus conducts an optimal power calibration (OPC).
In accordance with the OPC procedure, the microcomputer 100 controls the servo unit 70 and the drive unit 80 prior to recording of input data. In accordance with controlled operations of the servo unit 70 and drive unit 80, the optical pick-up unit 11 is controlled to read out a target writing power value Pind recorded in the form of 3-bit data W1, W2, and W3. FIG. 2 illustrates an example of the target writing power value recorded in the form of 3-bit data on the optical recording medium 10.
The microcomputer 100 then applies an adjustment signal to the optical driver unit 50 in a variable fashion. The adjustment signal is adapted to vary an optical power with reference to the read target recording power value, for example, 8 mW. FIG. 3 illustrates a variation in optical power with reference to a target recording power value. The optical driver unit 50 outputs a recording signal for test data at an optical drive power corresponding to the adjustment signal. In accordance with the recording signal, the optical pick-up unit 11 records test data onto a test recording area of the optical recording medium 10. FIG. 4 illustrates a recording signal test area A in a re-writable optical recording medium (CD-RW), along with a count area B for recording the number of test times, e.g., the number of times that the test data is recorded in the test area A.
The microcomputer 100 controls the pick-up unit 11 in a state, in which test data is recorded on the test area A of the optical recording medium 10, as shown in FIG. 4, in order to sequentially read out test data recorded several times. Each of the test data sequentially read is applied to the R/F unit 60 which, in turn, conducts a filtering and a waveform shaping for the test data, thereby reproducing that test data. FIG. 5 illustrates a reproduced signal for the test data recorded on the optical recording medium.
The microcomputer 100 then calculates the degree of modulation, based on the reproduced signal, and estimates a polynomial expression for a modulation degree curve (m=f(p)), using a curve filtering.
The modulation degree m corresponds to a value of I11T/ITOP (m=I11T/ITOP). Here, “I11T” represents the amplitude of the reproduced signal for an 11T signal, and “ITOP” represents a peak value of the 11T signal.
Next, a γ curve is derived using the estimated modulation degree curve “m=f(p)”.
FIG. 6 illustrates a modulation degree curve “m=(p)” and a γ curve “γ=g(p)” for detecting an optimum recording power value. Here, an expression “γ=p/m×f′(p)” is established.
Also, the value of a target γ recorded on the optical recording medium 10 is read out. Based on the read target γ value, an optimum optical power is derived. FIG. 7 illustrates respective data formats of γ and ρ values recorded on the optical recording medium 10.
The microcomputer 100 controls the optical driver unit 50 to output, for the input data, a recording signal according to the optimum optical drive power detected in the above mentioned procedure. The optical drive unit 50 applies, to the optical pick-up unit 11, the recording signal according to the optical drive power, thereby allowing a pulse-width-modulated signal to be recorded onto a program area of the optical recording medium 10.
In accordance with a conventional data recording method applied to the above mentioned optical recording/reproducing apparatus, however, the detection of the optimum optical drive power should be conducted using the result of the recording of test data when every data is to be recorded on the optical recording medium. That is, the detection of the optimum optical drive power should be repeatedly conducted for all data to be recorded. For this reason, there is a problem in that the data recording time is delayed.
In order to solve this problem, the following technique has been proposed.
According to the proposal the microcomputer 100, which is a microcomputer internally equipped with a memory, is configured to detect an optimum recording power value based on the recording and reproduction characteristics of test data, as mentioned above, and to record the detected optimum recording power value onto a designated particular area of an optical recording medium 10, along with an intrinsic recorder identification code for the optical recording/reproducing apparatus previously stored in the memory, that is, information for identifying the optical recording/reproducing apparatus, in order to reserve those information.
When an optical recording medium 10 is subsequently inserted into the recording/reproducing apparatus for recording of data, the microcomputer 100 reads out an optimum recording power value and an intrinsic recorder identification code from a particular area of the optical recording medium 10.
The microcomputer 100 then compares the read intrinsic recorder identification code with the intrinsic recorder identification code of the optical recording/reproducing apparatus. When the microcomputer 100 determines that the read intrinsic recorder ID code corresponds to the intrinsic recorder ID code of the optical recording/reproducing apparatus, it conducts recording of data using an optimum power identified from the optical recording medium 10 without conducting the procedure for detecting an optimum recording power.
However, where there is no optimum recording power value stored in the optical recording medium 10 or where the intrinsic recorder ID code read out from the optical recording medium 10 does not correspond to the intrinsic code of the recording/reproducing apparatus, the microcomputer 100 conducts the procedure for detecting an optimum recording power, that is, an OPC procedure, because the optimum power value stored in the optical recording medium 10 is that detected and recorded by a recording apparatus other than the above mentioned recording/reproducing apparatus. An optimum recording power value detected in the OPC procedure is then recorded onto the optical recording medium 10, along with the intrinsic recorder ID code of the recording/reproducing apparatus. Thereafter, desired data is recorded onto the optical recording medium 10 using the optimum power detected in the OPC procedure.
Thus, it is possible to more or less reduce the data recording time.
Meanwhile, where recording of data is repeated on a re-writable recording medium in an overwrite fashion, there may be a degradation at side portions of recording marks subjected to an image variation. As a result, a degradation in data recording characteristics may occur. In particular, when the recording apparatus overwrites data at a recording power level lower than that used in the previous data recording, the degradation in data recording characteristics becomes more severe, thereby resulting in increased errors in reproduced signals. FIG. 8 illustrates a relation of the amount of jitters involved in recorded data with respect to the number of data overwrite times. Also, FIG. 9 illustrates a degradation in reproduction characteristics varying depending on a variation in recording power between successive recording procedures.
The above mentioned problem is also involved in the method using the optimum power value along with the recorder ID code. That is, although recording of data is carried out using the power value derived in accordance with an OPC procedure when the recorder ID code detected from the optical recording medium is different from the identification code of the recording apparatus, it is difficult to expect satisfactory reproduction characteristics when the derived power value is not more than the power value used for the previous data recording, as shown in FIG. 9. The same problem may also occur where recording of data is carried out using the same power as the optimum power value for the data, previously recorded, without the execution of the OPC procedure when the recorder ID code detected from the optical recording medium corresponds to the identification code of the recording apparatus.
Due to such a degradation in reproduction characteristics, reproduction errors may frequently occur, thereby making it impossible to recover the recorded data.